• Introduction
• How they work
  • 1. The axle.
  • 2. The stack of laminations.
  • 3. The commutator/collector.
  • 4. The wire
  • 5. Holes or putty - Balancing methods
  • 6. Brushes
• Motors for the Eco 8
• Maintenance

Introduction

Whilst there are several key components in any helicopter, the one component that really makes a difference is the type of motor that powers the thing. The standard Eco 8 is just a basic kit and allows you to purchase any motor, speed controller and other components that suit your personal preference, however most people tend to buy the packaged deal when purchasing the Eco 8 helicopter, which includes the Ikarus “Sport” motor. This article looks at the various motor options available for the Eco 8, mainly concentrating on the brushed design.

How they work

There are two types of motors that are often used in electric model helicopters, brushed and brushless. The two vary in design, function and price. As a typical brushless set up can cost £250 – £350, it is generally out of the reach of the newcomer to the hobby, who tends to be on a fairly tight budget. This article will therefore deal with the standard brush type.

So what are the main parts to a quality brushed motor

1. The axle.

The axle is normally made of hardened stainless steel with a thickness of 3.14 mm. (0,125 inch) with a flat spot at one side for the pinion set screw. Very rarely nowadays we see axles without flat spots.

2. The stack of laminations.

The 3 pole stack is made up out of very thin "slices" of silicone steel, which are pressed together to a length between 21.5 ( minimum regulated size ) and 22.5mm. For protection against damage and rust and prevention of the sharp edges cutting the wire while winding, the stack is often coated.

There are various inside designs used, the most used are the straight or tapered leg (the part the wire is wound around) The difference in these designs is small but can make a difference to the performance of the motor, the more silicone steel material, the more punch/torque.

3. The commutator/collector.

This part is the most important part of the motor together with the brushes. Looking at the collector is easy to discover that it has 3 separated thin segments, which are made of pure copper. These segments are baked on a ceramic insulation material, which is pressed and/or glued on the axle.

4. The wire

The wire is wound around the 3 poles in such a way that it will react in the magnetic field created by the magnets when power is applied to the commutator. If the wire can move it will create 2 things: an unbalance and a possible short circuit in the wires. To protect the wire from moving on the stack the armature will often be dipped in a special corrosion preventing epoxy coating and heat hardened treated for maximum strength. The number of turns around each pole, and the number of strands of wire used generally dictate how the motor will perform. The Ikarus Sport motor has 23 turns of a single wire (referred to as a 23 single or 23 x 1)

5. Holes or putty - Balancing methods

Holes on top or /and epoxy putty on the side of the stack is the method used to balance the armature. This balance is necessary to increase the RPM and to increase the life of ball bearings and bushings.

6. Brushes

The last part is the end-bell, which house the brushes and springs. The end-bell fits over the top of the shaft and has the fixings for the power cables from the speed controller. The current is fed to the motor via a set of carbon brushes, which are held against the commutator by wire springs. Brushes vary in type and hardness and have a profound part to play in the performance of the motor.

Motors for the Eco 8

OK so now you know the components of the motor, what can you expect to get from them. Well in short, most motors will provide enough power to lift the heli off the ground with the right combination of batteries and pinion. The Ikarus motors work well on 8 cells with the stock 10 tooth pinion, however fitting a slightly larger main pinion can increase the head speed and the performance of the Eco dramatically.

The one thing you will notice is that the stock Ikarus motors are expensive, with the performance and power motors having an RRP of £60 and the Sport retailing at £40. Investigation has as yet not shown these motors to be anything special in terms of winds etc. But what alternatives are there, in a word – LOADS !

How cheap do you want to go, how about £4.50, that’s right less than a fiver will get a super motor that will give stacks of duration, and power. It’s called the Hurricane from Overlander Batteries. However you will need a 12 tooth main pinion if used with an 8 cell battery pack and 14 tooth pinion with 10 cells gives it a very spirited performance. The downside it that you can’t maintain the motor by cleaning or changing brushes etc. So it becomes a throw-away item when the performance drops off.

If you want something a bit more powerful and something that has limited service ability, then the next step is a “buggy” or 540 class motor. Most model shops will have a selection of motors for model cars, ranging from £10 - £100. The cheaper versions tend to have fixed end-bells so the only thing that can be done to maintain the motor is replacement brushes and cleaning the commutator using a comm Stick. For around £12 you can get a Team Orion Havok motor which using 10 tooth pinion and 8 cells will give a lively performance. A word of warning though, don’t go below a 21 turn single wind motor as the current drawn will fry a typical 35 – 40 amp speed controller. If you are after longer flight times, with less performance then a 27 turn single wind (often referred to as a stock motor) is ideal. If you spend a little bit more, say £20 you should be able to get a rebuildable motor that can be stripped down and cleaned.

Maintenance

Which ever motor you chose its efficiency will decrease as it is used as carbon deposits build up inside the motor and arching damages the copper on the commutator. If you have a rebuildable motor you should remove it from the Eco and dismantle it for cleaning after every 20 flights or so. Most motors are zero timed, however it’s worth making a mark in the end-bell and the can so they end up back in the same place after the strip-down. Un-clip the springs and remove the brushes, then undo the two screws securing the end-bell. Remove the end-bell and place to one side. Inside the can there will be a retaining disk, which needs to be rotated so the slots line up with the dimples on the inside of the can before it can be removed. Then remove the armature, checking to see if any small washers are left inside the can.

Now squirt some WD40 (damp start often used on cars) inside the can to release the carbon deposits. This may need repeating several times, with the application of a paper towel to wipe up some of the fluid. The can should then be rinsed in warm water and left in a warm location (airing cupboard is ideal) to dry. Now do the same to the end-bell and the armature, making sure you don’t lose any washers or insulators.

Once dry you can re-assemble the parts, however you should also polish up the commutator by placing 1000 grade wet and dry paper on the com and gently rotate it whilst applying pressure with your thumb and fore-finger. Always rotate in one direction and not back and forth. Now once assembled install a fresh set of brushes and re-align the timing marks, job done!

• Breaking in
• Cleaning

Breaking in

Get a 3V power source. 2 alkaline D cells or a 5V line from a converted PC power supply with a 55W halogen light bulb in series will do.

I let it run at this voltage for 36 - 48 hours. This gives a perfect contact surface area between the brushes and the com. I also put a cooling fan and heatsink on the motor at this point.. I did it with my sport motor and that thing never got hotter than 120 F!

Clean it thoroughlmy after it's run in

Cleaning

I cleaned it out every 5 or 6 flights by flushing it with the motor cleaner until it ran "clear" from the bottom of the motor. Then I'd just put a small drop of oil on each bearing and be ready for the next 5 flights or so. Spray brake cleaning fluid from your auto parts store can be used for cleaning too. The cheapest brand will do.

I also never cleaned it hot.. always let it cool to ambient temperature before hitting it with the motor cleaner. Learned this lesson the hard way after warping the com on my first Magnetic Mayhem Reverse.

I also throw out the stock brushes and install hard compound (P compound) brushes. They hold up to the current demands of the ECO much better.

• General Battery information
• Terminology
• Out of balance battery
• Fixing an Out of Balance pack - The C/10 charge theory
• Charging at higher rates
• Zapping Cells-
• The Biggest Problem With Battery packs
• Only Charge batteries Once a day.
• Memory Effect
• Cell types
  • Nickel Cadmium (NiCd)
  • Nickel Metal Hydride (NiMh)
  • Lithium Ion (LiIon)
  • Lithium Polymer (LiPoly)

General Battery information

This is not necessarily specific to any one battery type. This page is to help explain the different types of batteries used for E-Flight as well as give some general information. This was information that was posted in a thread on the Ikarus BBS and some information was gathered and put here. Thanks to everyone to added to the discussion.

Terminology

C = Capacity or charge current
1C = Charge the pack at 1x it's capacity (3000mAh at 3.0 amps, 2400mAh at 2.4amps)
C/10 = Charge at 1/10th the capacity (3000mAh at 300mAh, 2400 mAh at 240mAhs)
Lio = Lithium based battery cell. Lio-Polymers, Lio-Ion are examples
Out of balance battery - pack is when some of the cells in the pack still had some charge left in them while others have no charge remaining.
IR = Internal Resistance
Trickle Charge = A trickle charge is less than C/10 and is meant for continuous charging for standby devices such as cordless phones
Slow Charge = C/10
Peak charge = Charge at 1C and Slow or Trick after pack peaks.
Fast Charge = Charging above 1C

Out of balance battery

Pack is out of balance is when some of the cells in the pack still had some charge left in them while others have no charge remaining. So when you charged the pack three of the cells peaked before the others did. That would leave the other cells a little under charged. So when you ran the pack out the undercharged cells dumped before the fully charged ones causing the under charged cells to feel warm. Cells begin to really heat up when they reach their "dumped" point.

Fixing an Out of Balance pack - The C/10 charge theory

Just do a C/10 (c = capacity i.e. 2400mAh pack is charge 1c at 1.2A) charge for 14-16 hours, the magic of "slow charge" is that it equalizes the cells. As the cells fill up some will get full before others, but at the C/10 rate there is no danger of over charging because the cells that are full can safely dissipate the "over charge" as heat, without damage, giving the other cells time to fill up. This is also why it's a good idea to occasionally C/10 charge all your packs, in normal use over a number of cycles they will start to become unbalanced and the C/10 charge will rebalance them. Setting a C/10 trickle rate after a pack peaks will also do this, the pack will peak when the first cell or two does, but the others may not be quite full yet, if left at the C/10 trickle for some time after peak the cells will rebalance. Some people say that they see a reduction in power if the trickle charge after the pack has peaked, stating they perform best hot off the charger. This is not as noticed with NiCds but it does seem to be true for NiMHs, but Suspicions are it is temperature related as NiMHs always seem to perform better when warm and the time spent trickle charging will let them cool.

Charging at higher rates

This is to drive up the initial voltage of the pack. "Car jockeys" charge at high amp rates to get that extra edge at the start of a race. But the higher voltage only lasts for about 20-30 seconds and then the pack drops off to its normal 1.2 volts per cell. But in flying you don't need or want that higher short-term voltage. You want the pack to charge at a lower amp rate so it fully deep charges for long run out times.

Zapping Cells-

NiCad cells build up crystalline formations, as they are manufactured and later as they are cycled. These crystals cause tiny bridges to form between the plates inside the cell. The more crystal formations the harder it becomes for the cell to absorb and release energy effectively. This is refereed to as IR or Internal Resistance. A "Zapper" pretty much explains it's self. It's basically a transformer and huge capacitors that store up a very large charge and then releases it through the cell in a couple microseconds. This tends to shatter the crystals breaking down the IR in the cell and making it more efficient. Commercial zappers are very expensive and can pass as much as 30,000kva through a cell. There are less expensive "maintenance" zappers that put up to 90volts at up to 1kva through a cell to help keep crystals from building up.

There is still some debate on whether or not zapping actually does anything for NiMH though. There is also still discussion on whether or not "Zapping" cells will shorten the life. People have shown as much as a 14% improvement in NiCad cell performance with high current draw (above 40amps) applications. But again it may shorten the cell life and number of times the cells can be cycled.

The Biggest Problem With Battery packs

With our batteries is that they eventually go out of balance and depending on your charger's peak sensitivity, some cells will be overcharged while the others catch up, or the slow cells will not get fully charged and will be over discharged or even reverse charged as the pack runs down.

Only Charge batteries Once a day.

Batteries don't keep track of time, they don't know if it's today, tomorrow or yesterday. As long as you allow them to cool down before putting them back on charge, you can charge them as many times as you like. Of-course the more you use them the less time they'll last in terms of years, but not in terms of cycles.

Memory Effect

Nicads in every application suffer "memory effect" to varying degrees, the newer sintered cells are affected less but NiMh do not suffer this phenomenon at all. The problem with NiMh is that for a given current the output voltage is less than NiCd, because of the voltage drop across the higher internal resistance of NiMh cells. That's why one or two extra cells are added to increase the voltage when using NiMh. Note that some NiMh cells are becoming available whose internal resistance is approaching that of NiCd cells.

Cell types

Nickel Cadmium (NiCd)

NiCd cells can be charged at a pretty high rate. Many time NiCad packs are charged with a rating of up to 2.5 times their capacity. A 2400 mAh cell is thus charged at 6 Amps in 24 minutes. Chargers exist of up to 12A per hour (Robbe's latest). With non sorted packs you shouldn't go above 6A though. The differences between the cells will make the charger false peak and the pack will never be full.

Get a good charger that can handle both NiCd and NiMh cells. Make sure you can charge at least 16 cell packs and set your budget decide on the maximum charge rate. You are bound to charge larger packs sooner or later and a high charge rate will get the time to charge the pack down.

If you want to go above 16 cells, get a second 16 cell charger and split the pack up. Then charge the two packs simultaneously. Two 16 cell chargers are cheaper than one 32 cell charger. This is due to the fact that the power needed to charge big pack is pretty high. This power translates in special electronics and heat precautions.
Another advantage of having two chargers is that when you fly packs smaller than 16 cells, and you have 3 packs, you can fly indefinitely. There are always two packs charging while you fly with one. A good charger doesn't take more than 20 minutes to charge a pack. With a 10 minute flight, you can simply rotate the packs after every flight.

Nickel Metal Hydride (NiMh)

This type of cell has a much larger capacity than NiCd cells. A NiMh cell of 3300 mAh capacity is the same size as a NiCd cell of 2400 mAh. The disadvantage of these cells is that they can't handle bigger currents. For our applications of up to 25 Amps they are very usable. Nevertheless they tend to drop their voltage a bit more than NiCd cells. The latest generation of High Voltage NiMh cells have this a lot less.

Charging NiMh cells must be done a lot more careful than NiCd cells. Most manufacturers say that you shouldn't charge over 1C (1 time the capacity per hour), although many people report charging NiMh cells at 2C without a problem. Whether this over charging will shorten the life of the cells remains to be seen. To be safe it is recommended to stick with the 1C rule.

A few examples:
Panasonic 3300 mAh packs can be charged at up to 3.3 A
Sanyo 3000 mAh packs can be charged at up to 3 A
Sanyo TwiCell 1800 mAh AA cells can be charged at up to 1.8 A

Lithium Ion (LiIon)

These cells have lower weight and higher energy storage capability than NiCd or NiMh, but have a relatively low current delivery capacity of 2-4C. In addition, they must be charged at less than 1C, resulting in charging times of at least an hour. The result is that for high current applications like the Eco8, a number of packs must be paralleled to achieve the necessary total current capacity. Each LiIon cell has a nominal voltage of 3.6 volts vs the 1.2 volts of NiCd and NiMh, so 1/3 the number of cells is needed for the same voltage. Paralleling six packs of three 18650 cells (10.2v at 1400mAh/pack) would create a battery bank capable of delivering 25Amps at a 3C rate and would weigh 27oz (792gm) and provide 8400mAh. Total weight is about the same as a NiCd or NiMh pack, but the capacity is 2-4 times as much, translating into longer flight times.

The major disadvantage of Li-Ion is that they explode and catch fire when overcharged. Don't try to charge one on your NiCd/NiMh charger! A charger designed for Li-Ion cells will have the proper charge profile to prevent overcharging.

Another factor is that Li-Ion batteries age over time, regardless of whether they are used or not. A typical Li-Ion battery will last for a year and will typically need to be replaced in two years. A number of places on the Internet sell surplus Li-Ion battery packs, typically from cell phones or laptop computers. Many of these cells may have already past the two-year point at which their internal resistance prevents them from providing much of their energy for flying models.

Lithium Polymer (LiPoly)

If you're interested in longer flight times and a safer battery pack, check out the LiPoly cells that have recently become available. They are 3.6 volt cells and can deliver current at 4C rates. They are the lightest cells you can buy today, but are expensive. However, the additional flying time tends to offset the price, making them comparable to buying several packs of NiCd or NiMh cells. Paralleling four packs of three 2070mAh cells produces a battery bank that can deliver 33Amps, weighs 18.5oz (528gm), and provides 8200mAh. Creating a battery bank by paralleling two packs of three of the 3270mAh cells that could deliver 26Amps, weigh 13.5oz (384gm), and have a capacity of 6540mAh.

Charging LiPoly cells is similar to charging LiIon - you need a charger that can handle their special charging characteristics. The nice thing about these cells is that they are not prone to explosion and fire when overcharged - they swell and do get warm or hot. They are still not candidates for charging on your NiCd/NiMh charger. Only use the correct type of charger!

• Introduction
• Getting the material
• Building instructions
  • Building the Car part based regulation
  • Syringe based regulation
  • Installing your fridge compressor
• The final result
• Tips for using your vacuum press

Introduction

What the hell a step-by-step instruction to build a vacuum pump is doing on a site dedicated to the electric helicopter?...

I must admit that it may sound strange but I will list you some application that may bother the heli pilot you are. For example, you may use it when building your own self-made canopy, a new composite undercarriage (ask Bert) or a set of custom blade. In fact everytime you will need to press something for quite a long time.

This is often the case when you work on something using composite (such as carbon fiber, glass fiber tissue, Kevlar,...), you always need to press the different layer on a shape and keep them in place in order to let the epoxy polymerise.

People often use heavy loads, sand bags, their collections of magazines or anything in the neighboourhood looking heavy but they never obtain a regular and optimal pressure on all parts of the work. By using vacuum, you can apply the same high pressure on all parts. How can this be achieved?... Answer: by using athmospheric pressure! All you need to do is put your items inside a polyethylene plastic bag and use a vacuum pump to lower the pression inside the bag.

A depressure of -100 mbar gives a load of 100 kg per square meter, if you apply -500 mbar, you will end up pressing 1/2 ton per square meter. Our problem now is to get a vacuum pump and a regulation to do it. You can find some on the market but at a retail price that will make you think twice before buying it. Other solution is to build your own. The solution I will describe here has been validated and I will explain you how to build it for almost nothing.

Getting the material

In order to build your own vaccum pump you will need the following items:

1. One fridge compressor unit

   Fig.1 Fridge compressor unit

   Go to your local fridge resselers, they often offer to take the previous back when customer buy a new one. And they dont know what to do with them. Ask them if you cannot take one off. You will need a good cuting plier to cut in and out tubes. Please avoid using a metal saw to cut them because the metal dust can enter the tubes and give trouble later.

   Note

   Take care to let at least 10 cm of in and out tubing. Pay attention while handling the compressor they are often filled with oil. You must keep it inside. press the last centimeter of the tube to seal it for transport

2. One admission advance regulation valve OR one glass syringe

   This part can be found in almost all old engine (with no electronic advance regulation). This looks like a metallic can like a flying saucer with a tube on top.(crazy definition but I do not engineered these parts anyway) How does it work? It contains a rubber membrane that can move depending on the depression applied at the inlet tube. The more depression there is, the more the membrane moves. An iron wire is linked to the center of the membrane and moves with it.

   Fig.2 Vacuum valve front view

   Fig.3 Vacuum valve side view

   If you cannot find that part, you can go to your pharmacy and ask for a glass syringe (The bigger, The better). We can also use it for this job.

   Note

   Do not use plastic syringe, they are not adapted for this job.

3. One 220v. microswitch

   It should be strong enough to support the load of the fridge compressor unit you have. Speak about this with your electronic part reseller.

4. One manometer

   Fig.4 Fuel Pump Pressure vacuum manometer

   You will find this item in any car supply store. It is used to check fuel pump aspiration. It as generally scaled from -1 bar to + 5 bar stepped by 0.1 bar. It is really low cost item.

   Note

   This item is optionnal, but is useful to precisely set the depression value you want to apply. When using foam core forms, you should not apply too much vacuum or the form will collapse on itself. (Max depression for foam core is -0.4 bar, if you apply more, deformation may occur ruining your work.) Always perform some experiments before in order to know the limit of your materials.

5. Some meters of plastic tubing

   It should be strong enough not to squeeze on itself under vacuum.

6. A ping-pong ball

   I bet you are wondering what we gonna do with this ...

7. some plywood

   to build the box around the regulation to protect user from electric shock.

8. One spring + nuts and bolts

   you can canibalise one from a old camp bed or go to a outdoor shop to find spare ones.

9. One Bycicle wheel ray

   This will be used to replace the iron wire connection on the admission advance regulation valve. The original one is too short and the wheel ray is threaded with the same path.

Building instructions

There's two regulations possible, one using the car part and the other one using a glass syringe. Here below you will find:

• detailed instructions to build the car part one with some photos. a
• basic instructions to build the syringe regulation

Building the Car part based regulation

1. Understanding the principle

   Fig.5 Car part regulation principle

   The principle is easy to understand. When connected, the compressor will turn ON and begin pumping. As more and more vacuum is applied to the inlet of the valve, the iron wire moves back releasing pression on the micro switch. When the OFF position is reached , the compressor unit stops. Due to unavoidable leaks, the vacuum will lower little by little and the iron wire will come back pushing the microswitch ON, starting the compressor unit for a new cycle. The more the bolt retaining the spring is tightened, the more vacuum depression you will get.

2. Build a wooden box out of plywood in order to put all hazardous parts inside a secured area. Install the valve outside just letting the iron wire go inside. Bolt the microswitch to the base and connect the power wires to it (soldering is just fine). All you need is to install the bolt and spring and connect it to the iron wire coming from the valve. solder a push button guided to the switch by two piece of wood. Job is done...

   Fig.6 Car part regulation example

   Fig.7 Car part regulation bolt

3. Install your electric junctions in an isolated box on top of your wooden box. This will be easier for later maintenance.

   Fig.8 Car part regulation overview

Syringe based regulation

1. Understanding the principle

   Fig.6 Syringe regulation principle

   Principle is not very different from the car part based solution. The only limit here is that the system MUST be fixed verticaly and firmly attached due to the load. When connected, the compressor will turn ON and begin pumping. As more and more vacuum is applied to the inlet of the syringe, the piston moves up releasing pression on the micro switch. When the OFF position is reached , the compressor unit stops. Due to unavoidable leaks, the vacuum will lower little by little and the piston will come back due to the load in the basket pushing the microswitch ON, and starting the compressor unit for a new cycle. The more load in the basket, the more vacuum depression you will get.

2. To build this regulation, take care to fix the syringe firmly. It is best to fix it using collars (like tie-raps) over small strip of rubber cutted out of bycicle wheel tubes. Be careful not to brake your syringe. Take care to limit the piston move with one or two nails. It should only be able to move until the switch is fully pressed ON, not lower in order to avoid mechanical load on the switch.

Installing your fridge compressor

1. You should firmly install your fridge compressor on a wooden plate using the rubber damper you found when dismanteling it.
2. Normally you shoud have let 10 cm of tubing. The last centimeter flattened for transport. We can now cut the in and out tubes in a proper way. Use a tube cuting tool to shorten them to 8cm.
3. Identify the IN and OUT tubes by starting the compressor.
   Warning

   Some oil may be projected by the OUT tubes so keep yourself out of the way.
4. On the OUT tube, fix a 20 cm tube. Guide this tube verticaly on a wood stick and cover the end with the ping-pong ball. drill small holes in the ball so that the air can get out. This little ball will act as an oil recuperator.

   Fig.6 Ping-Pong ball installation

5. To the IN of the compressor you will fix the vacuum tube. On this tube you will add a "T" in order to get one tube to go to the inlet of the regulation and the other one to the bag. Optionaly you may add an other "T" to be able to add the manometer in the chain. But it can be a new source of leaks.

   Fig.6 Tube installation

6. Now seal all links using silicone and tie-raps. Let dry...
7. Proceed with the few tests. You should be able to fix most of the problem by yourself. if not, you can go to the Ikarus Eco8 forum and post your trouble.

The final result

If you have choosen to go for the Car Part version, you will end up with something looking like this:

Fig.6 Vacuum pump - lateral view

Fig.6 Vacuum pump - top view

Fig.6 Vacuum pump - front view

Tips for using your vacuum press

• Use only polyethylene plastic, this material cannot be glued using common epoxy glues. You will find this very useful when time to open bag will come.
• I use silicone to seal my bags. Others use window mastic but it is not as good.
• Sometimes, the plastic of the bag covers competely the pump tube thus stopping pump too soon. In order to avoid this case, here's a simple trick. Use a large wool string that you install all the way round your work inside the bag and put one of its end inside the vacuum tube. This will act as a air drain and will insure optimal depression repartition inside the bag
• Listen carefully to your bag sealing to detect leaks. You should track them to avoid unnecessary pumping.
• Most fridge compressor got a overheating protection, if it starts too often in a short period the motor may fall in secure mode. You will have to wait until relay cools down with cord unplugged from outlet.

• PET Soda Bottle
• Wrap around a stick
• Heat up
• Finishing

PET Soda Bottle

PET is short for Polyethylene Terephthalate and is a kind of polyester plastic. As it's a thermoplast it can be shaped using heat. Get a PET soda bottle out of the recycle bin and cut the top and bottom from it. Slice it open lengthwise so that you get a flat piece of thin plastic. Use your steel rule to cut a strip of about 3mm wide.
  

Wrap around a stick

First of all you need to get two pieces of tape ready. Then stick the piece of plastic to the top of the tape at a 45 degree angle. Check the second picture below. Wrap the tape around a stick. The diameter of the stick will define the diameter of the wire wrapper. Wrap the piece of plastic around the stick, maintaining a 45 degree angle. The sides do not have to meet. Leave a gap about the same width of the strip. When the whole strip is wrapped around the stick, fasten it with the second piece of tape.
 
 

Heat up

Get out a torch of some kind. I use a pen torch as it is just the right size. Don't use a candle. This leaves too much soot and does not disperse the heat enough. You have to go rather close to get the plastic to set and you risk melting it entirely. The trick is to apply just enough heat and never too much. An alternative I haven't tried is a heat gun used for removing paint. It should work nicely.
The aim is to heat up the plastic to that it gets above its plastisizing point of around 120 degrees Celcius. If you heat above 160 degrees Celcius, its melting point, you'll be left with a very thin strand of formless plastic that is useless. Be careful with the heat. Little bits at a time and certainly never too much.
It's very easy to know if you have applied enough as the edges of the plastic will start to curl up. Don't heat any more as you are already around the melting point. A little practice makes perfect.
 

Finishing

Remove the tape and slide the stick out of the helix. Test the spinginess of the wirewrapper. You'll be amazed at how far you can unwrap it, while it still returns to it's new shape.
Cut off the edges that were covered by the tape and thus not set. Admire your work and try it on your helicopter.

Use the wire wrapper to fasten the antenna to a skid.

• The clamp
• The supports
• Mounting the supports

The clamp

The first thing you need to do is measure the outer diameter of the brass or plastic tubes you want to use. A piece of snake tube from the tail servo lead is perfect.

Let's suppose the tube is 4mm thick. Take a piece of balsa the same thickness as the tube and cut out three squares each 5 by 5cm. Glue these pieces on top of each other, making sure you rotate the middle piece 90 degrees so that you get a piece of balsa plywood of 5 by 5cm. Try to bend it, you'll be amazed on how strong this is.

Draw a horizontal and a vertical line halfway so you find the center of the piece. Take out your compass or a piece of tail boom (from a previous crash) and draw a circle of 18mm diameter in the middle. Draw some extra lines 13mm and 17mm each side of the center line that runs parallel to the nerves of the top layer.

Cut the excess of the pieces by cutting along the lines 17mm from the center. Turn the piece by 90 degrees and cut 2mm outward of the circle.

Cut two pieces of 1mm plywood the size of the top of the clamp pieces. If you use 4mm tubes you will need two pieces of 12mm by 34mm. Glue them on top and on the bottom where the tailfin and the balls links will be.

Start up your drill press using a drill the same diameter as your tube (4mm in my example). Position your piece with the plywood pieces at the top and bottom. Drill through the plywood and the middle layer exactly at the position of the extra lines (13mm from center).

Use your scroll saw to cut the piece in two in a right angle to the holes you just drilled. Now it is very easy to cut out the two half circles. If the circle is a little rough use a piece of tail boom, wrap it in some thin sandpaper and sand it smooth. Don't take off too much.

Glue the brass or plastic tubes in the pieces. Decide what piece is going to be the bottom part and make sure you leave 1mm sticking out at the side of the plywood. If you don't do this, the ball links will be too close to the plywood.

Fit the pieces and sand them so that you have a gap between them. If you don't have a gap, you won't be able to tighten them sufficiently.

Cut two 2mm threaded rods to length (approx. 35 mm). Glue or solder a nut at one end thus creating a pretty long screw. Drill the horizontal fin at the appropriate places and put everything together according to the pictures.

Use a black felt pen to paint them.

You can download a PDF docment with a drawing of the tailfin here. Just print it with scaling or resizing OFF

The supports

Take two pieces of 5mm carbon tube, each 39cm long.

Use a 3mm drill to ream out the last 10mm of each end. Glue threaded push rod end pieces into these holes. Make sure they don't go deeper than 10mm.

Put plastic ball links on each end.

Mounting the supports

Drill a 2mm hole through the after landing gear at about 10mm out of the frame. Put a ball from a ball link through a 20mm M2 screw and stick it through the hole. Fasten it using a nut.

Click one end of the supports on the balls on the landing gear and the other end on the balls on the clamp.

Don't forget to use threadlock on every screw!